This invention relates to compact cylinders which are useful for a variety of purposes but which may preferably be of the general type illustrated in U.S. Pat. No. 4,167,134. As is customary, the end caps of the cylinder of the patent are secured by a mechanical bond provided by a metallic ring carried within a groove in the cylinder wall and bearing against a surface of the end cap for retaining same within the cylinder walls. An O-ring constructed of deformable material is carried within a groove within the end cap and provides a fluid seal. Such cylinders are useful in connection with robotic grippers, for example, and U.S. Pat. Nos. 4,566,727 and 4,492,400 are exemplary of such constructions.
Since such end caps may often move to a limited extent axially as provided by the mechanical bond, the end cap may strike the mechanical bonding member resulting in noisy operation. Since more than one groove must be provided within the cylinder walls and end caps for accommodating the mechanical bonding member and the sealing member respectively, the grooves may not be carried opposite each other but rather must be longitudinally spaced so that a relative thickness in the area of the end caps is necessitated.
Accordingly, an important object of the present invention is the provision of a more compact cylinder wherein the end caps can be made thinner because of opposed grooves provided in the walls of the cylinder and end caps forming a seat for single deformable members which serves both to bond the end caps entirely within the cylinder walls as well as a sealing member therebetween.
Another important object of the invention is the provision of a deformable resilient bond between the end caps and the cylinder walls adjacent their ends so as to function as a sound reducing means since there is no mechanical bond as afforded by a metallic ring as would result in noisy operation but rather the resilient deformable member which serves as a sealing and a bonding member also serves to cushion sound as well as shock.
Still another important object of the invention is the provision of a tapered ramp formed by a substantially conical surface at the open end of each of the caps facilitating assembly by avoiding twisting of the O-ring together with a retaining ridge which extends inwardly short of a center line of the O-ring and beyond the initial groove surface of the cylinder to deform the ring in such a way as to provide even greater force requirements for dislodging the ring in an outward direction than forces required to dislodge the end caps of the other embodiments herein.